Efficient service advertisement and discovery in a networking environment

ABSTRACT

A local device broadcasts a service advertisement in a wireless network, where the service advertisement includes one or more service identifiers (IDs) identifying one or more services being advertised and an availability schedule of the local device. Optionally, the local device reduces power to at least a portion of the local device and wakes up at a time according to the availability schedule. The local device listens in the wireless network according to the availability schedule of the local device. In response to a service request received from a remote device during the availability window, the local device transmits a service response to the remote device. The service request includes one or more service IDs identifying one or more services being inquired by the remote device and the service response includes detailed information associated with one or more services identified by the one or more service IDs.

RELATED APPLICATIONS

This application is a continuation application of, and hereby claimspriority under 35 U.S.C. §120 to, U.S. patent application Ser. No.12/796,513, entitled “Efficient Service Advertisement and Discovery in aPeer-to-Peer Networking Environment,” by inventors Pierre Vandwalle,Tito Thomas, and Charles F. Dominguez, filed on 8 Jun. 2010, whichclaims priority to U.S. provisional patent application No. 61/289,689,entitled “Mechanism for Efficient Service Advertisement and Discovery ina Wireless Peer-to-Peer Networking Environment,” by inventors PierreVandwalle, Tito Thomas, and Charles F. Dominguez, filed 23 Dec. 2009,which are incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments of the invention relate generally to the field ofpeer-to-peer networking; and more particularly, to service advertisementand service discovery in a peer-to-peer networking environment.

BACKGROUND

Devices such as electronic devices, computing systems, portable devices,and handheld devices have software applications such as gameapplications. Some of these applications are shared—for instance,multiple devices can participate in a game application in acollaborative fashion. The shared features of an application can bereferred to as services. Before a device can use a service offered byanother device, the participating device (the discoverer) has todiscover such a service available on a network. Services are advertisedby a remote device (i.e. the advertiser) on the network.

Various discovery techniques are available for electronic devicesconnected to, or attempting to connect to a network. These discoverytechniques typically involve use of a network protocol to determine whatdevices and/or services are available through a network connection.These discovery techniques are useful for many situations. However, incertain situations, these discovery techniques are not optimal.

Typically, each device in a network is configured to periodically scanand/or advertise a service in the network according to commonly knownscanning and advertising schedule, such as, for example, in a 100millisecond (ms)-800 ms period range. When there are many devices in thenetwork closely located, such a scanning and/or advertising strategy maynot be efficient as there may be heavy communications channelcongestion, which results in devices taking a long period of time todiscover a service of another device and/or to advertise a service. Insuch a scenario, additional time would need to be spent scanning toensure reliable service discovery. Spending additional time scanningconsumes a larger amount of power, which is a critical resource on aportable electronic device. Further, frequent discovery scanning andadvertisement transmission may themselves consume more power, which isimportant to a portable device. There has been a lack of efficient wayto optimize the service discovery and/or advertisement for portabledevices.

SUMMARY OF THE DESCRIPTION

According to some embodiments, a service discovery and advertisementmechanism is utilized to enable a device (e.g., electronic portabledevice such as a notebook, cellular/smart phone, media player, apersonal digital assistant (PDA), or a combination thereof) toefficiently discover and/or advertise one or more services in a wirelessnetwork (e.g., IEEE 802.11 or WiFi, personal area network such asBluetooth compliant network).

In one embodiment, when a first device advertises one or more servicesin a wireless network, the first device broadcasts or multicasts anadvertisement message (also simply referred to as an advertisement) inthe network, where the advertisement includes one or more serviceidentifiers (e.g., hashes), each identifying a particular servicepotentially available from the first device. The advertisement furtherincludes information regarding availability, such as an availabilityschedule, of the first device in which the first device will listen onthe network for any service requests about the advertisement.Thereafter, the first device may turn off or reduce power for at least aportion, such as a radio frequency (RF) portion (e.g., transceiver,antenna), of the first device until a subsequent certain time periodaccording to the availability information (e.g., availability schedule).Alternatively, the first device can perform some other tasks during thattime period.

When a second device on the network receives the advertisement, thesecond device can determine whether it is interested in acquiring one ormore of the services advertised from the first device based on theservice identifiers in the advertisement. If interested, the seconddevice can transmit a service request to the first device using theavailability information of the first device, where the service requestincludes the service identifier of one or more selected services. Forexample, the second device may transmit the service request according tothe availability schedule of the first device (e.g., during the firstdevice's availability window when the first device is listening). Inresponse to the service request, the first device can transmit moredetailed information about the requested services to the second device.

According to another embodiment, each device in the network isconfigured to monitor the operating environment of the respective deviceas well as network traffic in the network. Based on the result of themonitoring, a device may adjust its advertisement period and/or servicediscovery period dynamically. For example, if a device has a littlebattery life remaining, the device may reduce the frequency of theservice advertisements and service discovery (e.g., increase the serviceadvertisement and/or discovery periods). As another example, if it isdetermined that communications channel congestion is relatively high,for example, due to a large number of devices in the network, a devicemay also adjust the service advertisement and/or discovery periodsaccordingly (e.g., increase the service advertisement and/or discoveryperiods to avoid congestion collapse of the network).

In one embodiment, the service advertisement period and/or servicediscovery period are calculated based on multiples of a predeterminedbase value. However, the service discovery period is configured not tobe multiples of the service advertisement period, or vice versa. As aresult, an advertiser and/or a discoverer can calculate their ownservice advertisement period and/or service discovery periodindependently; but an advertisement from an advertiser will still becaptured by a discoverer over a period of time dependent upon thespecific calculation of the service advertisement period and/or servicediscovery period.

According to a further embodiment, multiple devices that are capable ofadvertising one or more services may coordinate with each other toselect one or more of devices to advertise the services on behalf ofother devices. Such a device acts as a group advertiser. A device may beselected as a group advertiser according to a variety of parameters(e.g., a battery condition, etc.), which are monitored by the monitoringlogic of the respective device. A device may operate as an advertiserthat advertises its own services and/or a group advertiser thatadvertises services of other devices in the network. A device may alsooperate as an advertiser for advertising its own services, as well asbeing an advertisee having one or more of its own services to beadvertised by another device. A device may also operate as an advertiseeonly that relies on another device for advertising its services.

Other features of the present invention will be apparent from theaccompanying drawings and from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 is a network configuration which may be implemented with anembodiment of the invention.

FIG. 2 is a block diagram illustrating an example of an electronicdevice according to one embodiment of the invention.

FIG. 3 is a flow diagram illustrating an example of a serviceadvertisement transaction flow according to one embodiment.

FIG. 4 is a timeline diagram of a service advertisement according to oneembodiment.

FIG. 5 is a block diagram illustrating an example of an advertisementmessage according to one embodiment.

FIG. 6 is a flow diagram illustrating an example of a method foradvertising a service according to one embodiment.

FIG. 7 is a flow diagram illustrating an example of a method fordiscovering a service according to one embodiment.

FIG. 8 is a block diagram illustrating an electronic device according toanother embodiment of the invention.

FIG. 9 is a timeline diagram illustrating an advertisement period anddiscovery period according to one embodiment.

FIG. 10 is a flow diagram illustrating a method for advertising aservice according to another embodiment of the invention.

FIG. 11 is a flow diagram illustrating a method for discovering aservice according to another embodiment of the invention.

FIG. 12 is a block diagram illustrating an electronic device accordingto another embodiment of the invention.

FIGS. 13A-13C are transitional diagrams illustrating examples oftransitions of devices among advertising operating states according tosome embodiments of the invention.

FIG. 14 is a block diagram illustrating a group advertisement messageaccording to one embodiment of the invention.

FIG. 15 is a flow diagram illustrating a method for a device to requestthat another device act as a group advertiser and advertise services onits behalf.

FIG. 16 is a flow diagram illustrating a method for a device to become agroup advertiser and start advertising services on behalf of anotherdevice.

FIG. 17 is a flow diagram illustrating a method for selecting a groupadvertiser according to one embodiment of the invention.

FIG. 18 shows an example of a data processing system which may be usedwith one embodiment of the present invention.

DETAILED DESCRIPTION

Various embodiments and aspects of the inventions will be described withreference to details discussed below, and the accompanying drawings willillustrate the various embodiments. The following description anddrawings are illustrative of the invention and are not to be construedas limiting the invention. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentinvention. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present inventions.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin conjunction with the embodiment can be included in at least oneembodiment of the invention. The appearances of the phrase “in oneembodiment” in various places in the specification do not necessarilyall refer to the same embodiment. The processes depicted in the figuresthat follow are performed by processing logic that comprises hardware(e.g. circuitry, dedicated logic, etc.), software, or a combination ofboth. Although the processes are described below in terms of somesequential operations, it should be appreciated that some of theoperations described may be performed in a different order. Moreover,some operations may be performed in parallel rather than sequentially.

Definitions

-   -   Advertiser—a device advertising one or more of its own services.    -   Group advertiser—a device advertising one or more services on        behalf of one or more other devices. Group advertisers also        advertise their own services, if they have any.    -   Advertisee—a device whose services are being advertised by        another device on the network (i.e. by a group advertiser, not        including itself).    -   Discoverer—a device that is trying to discover one or more        services on the network.    -   Availability Window—a period of time in which an device is        available and listening on the network, and is capable of        responding to service discovery requests, advertisement        requests, and other requests.    -   Availability Schedule—the times in which a device will be        available to respond to service requests. Included in        advertisement messages, this indicates the times and widths of a        device's availability window(s).    -   Advertisement/Advertisement Message—a broadcast/multicast frame        periodically sent by an advertiser that contains information        about services it has available.    -   Group Advertisement/Group Advertisement Message—a        broadcast/multicast frame periodically sent by a group        advertiser that contains information about its own services (if        any), as well as services available on other devices on the        network.    -   Advertisement Request/Advertisement Request Message—a message        sent by a device to another device requesting that the recipient        acts as a group advertiser and advertise services on behalf of        the sender.    -   Advertisement Response/Advertisement Response Message—a message        sent by a device to another device in response to an        advertisement request message, indicating whether the sender        will honor the initial request message and act as a group        advertiser.    -   Service Request/Service Request Message—a message sent by a        discoverer to an advertiser requesting detailed information        about service(s) matching the supplied ID(s).    -   Service Response/Service Response Message—a message sent by an        advertiser/group advertiser to a discoverer supplying detailed        information about one or more services.    -   Advertisement Period—the interval of time between successive        transmissions of an advertisement frame by an advertiser.    -   Discovery Period—the interval of time between successive        discovery attempts by a discoverer.

FIG. 1 is a network configuration which may be implemented with anembodiment of the invention. Referring to FIG. 1, network configuration100 includes multiple electronic devices 101-103 communicatively coupledto network 104, which may be a wireless network such as a IEEE 802.11(e.g., WiFi) or a personal area network (PAN) compliant network (e.g.,Bluetooth). Any one of devices 101-103 may be any of portable devices,such as, for example, a portable computing device (e.g. notebook/netbookcomputers such as MacBook™ from Apple Inc. of Cupertino, Calif.), atablet PC (e.g., an iPad™ from Apple Inc.), a cellular/smart phone(e.g., iPhone™ from Apple Inc.), a media player (e.g., iPod™ from AppleInc.), a PDA, a copier/printer/scanner/modem/facsimile device, or acombination thereof. Alternatively, any one of devices 101-103 may be adesktop computer or other non-portal devices having a wirelesscommunications interface (e.g., a built-in or plugged-in transceiver orRF frontend) that is capable of wirelessly communicating with anotherdevice in a wireless network.

Each of devices 101-103 includes service advertisement logic (e.g.,logic 105-107 respectively) and service discovery logic (e.g., logic108-110 respectively), which may be implemented in hardware, firmware,software, or a combination thereof. Service advertisement logic isresponsible for advertising one or more services of a local device innetwork 104 while service discovery logic is responsible for discoveringone or more services available from one or more remote devices innetwork 104. Devices 101-103 may advertise and/or discover one or moreservices in network 104 using a variety of wireless communicationsprotocols, such as, for example, WiFi or Bluetooth compliant protocols.Further detailed information concerning service discovery using apersonal area network protocol can be found in a co-pending U.S. patentapplication Ser. No. 12/405,130, entitled “Service DiscoveryFunctionality Utilizing Personal Area Network Protocols”, filed Mar. 16,2009, which is incorporated by reference in its entirety.

The purpose of an advertisement of a service from one device (alsoreferred to as an advertiser) is to inform other devices in a network,or to enable other devices (also referred to as discoverers) in thenetwork to discover that the particular service is potentially availablefrom that particular device. Also note that throughout this application,embodiments of the present application will be described in a wirelessnetworking environment; however, it will be appreciated that suchembodiments can also be applied in a wired networking environment.

In one embodiment, when a first device, in this example device 101,advertises one or more services available in a wireless network, theservice advertisement logic 105 of the device 101 broadcasts ormulticasts an advertisement message (also simply referred to as anadvertisement, or a service advertisement) in network 104, where theadvertisement includes one or more service identifiers (IDs), eachidentifying a particular service potentially available from device 101.A service identifier may be represented by a hash value constructedusing a variety of hash algorithms (e.g., SHA-1 or MD5). A hash valuemay be generated based on data representing a signature or certaincharacteristics of a particular service. The advertisement furtherincludes availability information, such as the availability schedule ofdevice 101, that device 101 will use to set its availability window,when it will listen in network 104 for any service inquires for theadvertisement from other devices (e.g., devices 102-103). Thereafter,device 101 may turn off or reduce the power for a certain portion ofdevice 101, such as, for example, at least the radio frequency (RF)portion (e.g., transceiver, antenna) of device 101 until a subsequentcertain time period according to the availability information associatedwith device 101. Alternatively, device 101 may in turn perform othertasks without transmitting or listening in network 104.

When a second device, in this example device 102, in the networkreceives the advertisement broadcast from device 101, based on theservice identifiers in the advertisement, device 102 can determinewhether it is interested in acquiring further detailed information ofthe advertised service from device 101. If so, according to oneembodiment, device 102 can transmit a service request to device 101according to the availability schedule of device 101 (e.g., during oneof device 101's availability windows when device 101 is listening),where the service request includes one or more service identifiers ofone or more selected services. In response to the service request,device 101 can transmit more detailed information of the requestedservices (e.g., device 102). That is, a service ID may merely indicate aservice potentially available from an advertiser. In order to confirmsuch a service, a discoverer has to acquire further detailed informationfrom the advertiser through a service request and response protocol.

According to another embodiment, each of devices 101-103 in the network104 is configured to monitor operating environment of the respectivedevice, as well as network traffic in the network. Based on themonitoring result, a device may adjust its service advertisement period(also simply referred to as an advertisement period) and/or servicediscovery period (also simply referred to as a discovery period)dynamically. For example, if the battery of device 101 is running low,device 101 may reduce the transmitting and listening frequency ofservice advertisement and service discovery (e.g., increase the serviceadvertisement and/or discovery periods). Another example, if it isdetermined that communications channel congestion is relatively high,for example, due to a large number of devices in the network, device 101may also adjust the service advertisement and/or discovery periodsaccordingly (e.g., increasing the advertisement and/or discoveryperiods).

In one embodiment, a service advertisement period and/or servicediscovery period are calculated based on one or more multiples of apredetermined base value. However, a service discovery period may not beconfigured as a multiple of a service advertisement period, or viceversa. As a result, an advertiser and a discoverer can calculate theirown service advertisement period and/or service discovery periodindependently; but an advertisement from a advertiser (e.g., device 101)will still be capable of being captured by a discoverer (e.g., device102) over a period of time. In addition, because of the fact that aservice advertisement period is not a multiple of a service discoveryperiod or vice versa, each of the devices in the network can adapt theirown period prior to establishing any communication among them, based onits own perception of the network conditions set forth above.

According to a further embodiment, devices 101-103 may coordinate witheach other to select one or more of devices to advertise the services onbehalf of other devices. For example, device 101 may be selected as agroup advertiser according to a variety of parameters (e.g., a batterycondition, etc.), which are monitored by a monitoring logic of thedevice, for advertising services for device 102 and/or device 103.Device 101 may operate as a group advertiser that advertises its ownservices and services of devices 102-103 in the network. Device 101 mayalso operate as an advertiser for advertising its own services, as wellas an advertisee having one or more services to be advertised by anotherdevice (e.g., devices 102-103). Device 101 may also operate as anadvertisee only that relies on another device (e.g., devices 102-103)for advertising its services.

Note that throughout this application, the term of “service” can be abroad range of services including, but not limited to, printingservices, local area network (LAN) access services, wide area network(WAN) access services, cellular telephone services, data storageservices, and/or application services (e.g., media playback, games,collaborative document creation services, recording services, etc.)

Efficient Service Advertisement and/or Discovery Mechanisms

FIG. 2 is a block diagram illustrating an example of an electronicdevice according to one embodiment of the invention. For example,electronic device 200 may be implemented as a part of any one of devices101-103 of FIG. 1. Referring to FIG. 2, device 200 includes, but notlimited to, service advertisement unit 201, service discovery unit 202,user interface unit 203, service management unit 204, storage device205, one or more processors or processor cores 206, network interfaceunit 207, and memory 208 coupled to each other via bus, interconnect, ormesh 209.

Processor 206 may be any kind of microprocessors, which may be a singleprocessor, multiple processors, or multiple processor cores. Networkinterface unit 207 may be part of an RF frontend including, but is notlimited to a wireless transceiver and an antenna or a modem, etc.Alternatively, network interface unit 207 may also include a wiredcommunications interface, such as Ethernet port, a universal serial bus(USB) or Firewire™ port. Memory 208 may be any kind of random accessmemory (RAM), which is typically implemented as a volatile memory. Userinterface unit 203 may include a display device, an input device (e.g.,keyboard, a touch pad, a touch screen, a stylus device, or a combinationthereof), and an audio and/or video interfaces, etc.

Service advertisement unit 201 is responsible for advertising one ormore services available or provided by device 200. For example, serviceadvertisement unit 201 may be implemented as a part of any one ofservice advertisement logic 105-107 of FIG. 1. In one embodiment,service advertisement unit 201 is configured to advertise, via networkinterface unit 207, one or more services by broadcasting or multicastingan advertisement in the network (e.g., network 104 of FIG. 1) accordingto an advertisement schedule (e.g., advertisement period). Anadvertisement may include one or more service identifiers (IDs)identifying a service that is potentially provided by device 200. Aservice identifier may be generated by service manager 204 and stored instorage device 205 as a part of service identifiers 210. In oneembodiment, a service identifier includes a hash value generated byservice manager 204 according to a variety of hash algorithms, such as,for example, SHA-1 or MD5 algorithms.

Alternatively, a service identifier may be represented by a particularbit of a bitmask, where a bitmask includes one or more bits having apredetermined logical value, each representing a particular service. Forexample, the location of a particular bit of a bitmask is used toindicate a particular service that is potentially available from anadvertiser, where the bitmask is broadcast in the network via anadvertisement, similar to the techniques disclosed in co-pending U.S.patent application Ser. No. 12/687,814, entitled “Efficient ServiceDiscovery for Peer-to-Peer Networking Device,” filed Jan. 14, 2010,which is incorporated by reference herein in its entirety.

Again, a service ID may merely indicate a service potentially availablefrom an advertiser. In addition, a hash (service ID) can possiblyrepresent multiple services as there may be a collision where multipleservices are hashed to the same value. In order to confirm such aservice, a discoverer has to acquire further detailed information fromthe advertiser through a service request and response protocol.Advertising a potential service by broadcasting or multicasting a hashvalue representing such a potential service, and providing detailedinformation about the service only in response to a specific request forsuch a service, greatly reduces the network traffic involved in serviceadvertisement and discovery.

The service manager 204 is also responsible for maintaining or managingservice information 211 associated with services available from device200, which may be stored in storage device 205. Storage device 205 maybe implemented as any kind of memory devices or disks and accessed viaany kind of file systems. Service manager 204 may also generate andmaintain a list of services available in the network, including servicesadvertised by device 200 and by other devices in the network. The listof services can be periodically updated in response to a result of aservice discovery operation performed by service discovery unit 202.

Similarly, service discovery unit 202 is responsible for discovering oneor more services available from the network, which may be advertised byone or more other devices in the network. For example, service discoveryunit 202 may be implemented as a part of any one of service discoverylogic 108-110 of FIG. 1. In response to an advertisement from a remotedevice, service discovery unit 202 is configured to communicate, vianetwork interface unit 207, with the remote device to acquire furtherdetailed information of the services and may generate or update a listof services that are available from the network, which may be stored aspart of service information 211.

FIG. 3 is a flow diagram illustrating an example of a serviceadvertisement transaction flow according to one embodiment. For thepurpose of illustration, it is assumed that both local device 301 (as anadvertiser) and remote device 302 (as a discoverer) have similar oridentical infrastructure as device 200 of FIG. 2. Referring to FIG. 2and FIG. 3, according to one embodiment, after receiving anadvertisement from a service advertisement unit of device 301 viatransaction 303, a service discovery unit of device 302 compares theservice IDs in the advertisement request with the ones locally generatedvia operation 304. If device 302 is interested in the advertised serviceor services, the service discovery unit of device 302 transmits aservice request to device 301 via transaction 305, including one or moreservice identifiers identifying one or more services that device 302 isinterested in. In response to the service request, the serviceadvertisement unit of device 301 transmits a service response to device302, including detailed information of one or more services requestedvia transaction 306. Note that a service identifier can merely indicatethat a service is potentially available from device 301. In order toobtain detailed information of the potential service, the discoverer hasto acquire detailed information by transmitting a service request basedon the service identifier. Device 302 then compares the returned serviceinformation against the local list of desired services via transaction307. If any of the services match devices 301-302 may participate in theservices (e.g., playing games in a collaborated fashion) via transaction308.

According to one embodiment, referring back to FIG. 2, when advertisinga service, an advertisement generated by service advertisement unit 201further includes an availability schedule of an advertiser, in thisexample, of device 200. In one embodiment, the availability scheduleincludes the start of the next availability window from the time of theadvertisement was transmitted and the length of the window (e.g.,duration of the availability window). That is, an advertiser may onlylisten in the network during a specific period of time. When adiscoverer receives an advertisement, the discoverer may schedule atransmitting time slot according to the availability schedule of theadvertiser, during which the discoverer transmits a service request tothe advertiser during one of the advertisers' availability windows.Otherwise, either or both of the advertiser and discoverer can turn offor reduce power to at least a portion (e.g., wireless transceiver or RFfrontend) of the respective device, for example, by a power managementunit of the respective device (not shown). Note that some or all of thecomponents as shown in FIG. 2 may be implemented in hardware, firmware,software, or a combination thereof.

FIG. 4 is a timeline diagram of a service advertisement according to oneembodiment. Referring to FIG. 4, when an advertiser (e.g., device 200)advertises a service, in one embodiment, the advertiser may transmit anadvertisement at time 401, where the advertisement includes anavailability schedule having an interval until the next availabilitywindow start 402 and duration of the next availability window 403. Thatis, after transmitting the advertisement at time 401, the advertiser mayturn off or reduce power to at least a portion of the device, such as,for example, an RF frontend of the device. The advertiser then may turnthe power back on at the next availability window for duration 403,during which a discoverer may communicate with the advertiser to acquirefurther detailed information of a particular service or services. As aresult, the power consumption of the advertiser may be reduced. Duringthe availability window, the advertiser may receive a service requestfrom a discoverer and replies with a service response having detailedinformation of the requested service or services.

Similarly, after a discoverer receives an advertisement, the discoverermay also turn off or reduce power to at least a portion of the deviceand wake up according to the next availability window of the advertiserfor transmitting a service request to the advertiser. As a result, thepower consumption of the discoverer may also be reduced.

FIG. 5 is a block diagram illustrating an example of an advertisementmessage according to one embodiment. Referring to FIG. 5, advertisement500 includes, but not limited to, a header 501, Availability WindowStart 502, Availability Window Length 503, number of service IDs 504,and one or more service IDs 505. In one embodiment, a service ID isrepresented by a hash value, which represents a possible service to beadvertised. Generally speaking, a hash (service ID) can possiblyrepresent multiple services as there may be a collision where multipleservices are hashed to the same value. Note that the format and fieldarrangement of advertisement 500 is shown for illustration purpose only;other formats or fields arrangement may also be implemented.

FIG. 6 is a flow diagram illustrating an example of a method foradvertising a service according to one embodiment. Note that method 600may be performed by processing logic which may include hardware,firmware, software, or a combination thereof. For example, method 600may be performed by service advertisement unit 201 of FIG. 2. Referringto FIG. 6, at block 601, an advertisement is constructed within a localdevice (e.g., an advertiser), including a next availability window startperiod, availability window length, a number of service IDs (e.g.,hashes), and the actual service IDs. Each service ID represents aservice potentially offered by the local device. At block 602, theadvertisement is broadcast or multicast by the local device in awireless network.

At block 603, the local device may optionally turn off or reduce powerto at least a portion of the device and wakes up at the time accordingto the next availability window specified in the advertisement requestat block 604. At block 605, during the availability window, the localdevice listens and receives a service request from a remote device overthe network in response to the advertisement. The service requestincludes one or more service IDs representing one or more servicesinquired by the remote device. The one or more service IDs may beselected from those presented in the advertisement previously broadcastor multicast from the local device. In response to the service request,at block 606, the local device transmits a service response to theremote device, including detailed information of the services requestedin the service request.

FIG. 7 is a flow diagram illustrating an example of a method fordiscovering a service according to one embodiment. Note that method 700may be performed by processing logic which may include hardware,firmware, software, or a combination thereof. For example, method 700may be performed by service discovery unit 202 of FIG. 2. Referring toFIG. 7, at block 701, a local device (e.g., a discoverer) receives anadvertisement from a remote device over a network. In response to theadvertisement, at block 702, the local device extracts from theadvertisement a next availability window start, availability windowlength, and one or more service IDs (e.g., hashes) identifying one ormore services advertised by the remote device. At block 703, the localdevice may optionally turn off or reduce power to at least a portion ofthe device and wake up at certain time according to the nextavailability window specified in the advertisement. At block 704, thelocal device transmits a service request to the remote device, where theservice request includes one or more service IDs (e.g., hashes)identifying one or more services to be inquired. At block 705, a serviceresponse is received from the remote device during the availabilitywindow of the remote device, where the service response includes moredetailed information of the inquired services.

Service Advertisement/Discovery with Dynamic Advertisement/DiscoveryPeriods

According to some embodiments, the advertisement period and discoveryperiod may be dynamically adjusted based on the operating conditionsand/or user behaviors at the point in time. According to one embodiment,each device in the network is configured to monitor the operatingenvironment of the respective device, as well as network traffic in thenetwork. Based on the result of the monitoring, a device may adjust itsadvertisement period and/or service discovery period dynamically. Forexample, if the battery of a device is running low, the device mayreduce the frequency of the service advertisement and service discovery(e.g., increase the service advertisement and/or discovery periods).Another example, if it is determined that communications channelcongestion is relatively high, for example, due to a large number ofdevices in the network, a device may also adjust the serviceadvertisement and/or discovery periods accordingly (e.g., increasing theservice advertisement and/or discovery periods to avoid congestioncollapse of the network).

In one embodiment, a service advertisement period and/or servicediscovery period are calculated based on multiples of a predeterminedbase value. However, a service discovery period may not be multiples ofa service advertisement period, or vice versa. As a result, anadvertiser and a discoverer can calculate their own serviceadvertisement period and/or service discovery period independently;however, an advertisement request of an advertiser is still capable ofbeing captured by a discoverer over a period of time dependent upon thespecific calculation of the service advertisement period and/or servicediscovery period.

FIG. 8 is a block diagram illustrating an electronic device according toanother embodiment of the invention. For example, device 800 may beimplemented as any one of devices 101-103 of FIG. 1. Referring to FIG.8, similar to device 200 of FIG. 2, device 800 includes, but not limitedto, a service advertisement unit 201, service discovery unit 202, a userinterface unit 203, a service management unit 204, a storage device 205for storing service identifiers 210 and service information 211, one ormore processors or processor cores 206, a network interface unit 207, amemory 208, and a user interface unit 203 coupled to each other via abus, interconnect, or mesh 209. These components have identical orsimilar functionalities as those shown in FIG. 2 and thus, certainreference numbers are retained from FIG. 2.

In addition, according to one embodiment, device 800 includes operatingenvironment monitoring unit 801 and advertisement and/or discoveryperiod or schedule calculator 802. In one embodiment, operatingenvironment monitoring unit 801 is configured to monitor the operatingenvironment of device 800, as well as network traffic in the network.Based on the result of the monitoring, advertisement/discovery periodcalculator 802 is configured to adjust the advertisement period and/orservice discovery period dynamically. For example, if device 800 has alesser battery life remaining (monitored by monitoring unit 801),advertisement and/or discovery period or schedule calculator 802 mayreduce the frequency of the service advertisement and service discovery(e.g., increase the service advertisement and/or discovery periods).Another example, if it is determined that communications channelcongestion is relatively high, for example, due to a large number ofdevices in the network or within a predetermined proximity,advertisement and/or discovery period calculator 802 may also adjust theservice advertisement and/or discovery periods accordingly. Furthermore,the advertisement and/or discovery periods may also be adjusted based onthe types of applications to be shared and user behaviors (e.g., activeusers), etc.

In one embodiment, a service advertisement period and/or servicediscovery period are calculated based on one or more multiples of apredetermined base value. However, a service discovery period may not beone or more multiples of a service advertisement period or vice versa.As a result, an advertiser and a discoverer can independently calculateand/or adjust the advertisement period and/or discovery period based onthe local environment. In addition, because of the fact that a serviceadvertisement period is not a multiple of a service discovery period, orvice versa, each of the devices in the network can adapt their ownperiod without establishing any communication among them based on itsown perception of the network conditions set forth above.

FIG. 9 is a timeline diagram illustrating an advertisement period anddiscovery period according to one embodiment. Referring to FIG. 9,timeline 900 represents an advertisement period and timeline 950represents a discovery period. For the purpose of illustration, theadvertisement period is calculated based on 3 times of a predeterminedbase value while the discovery period is calculated based on 4 times ofthe predetermined base value. As shown in FIG. 9, although theadvertisement messages are broadcast at a different time and a differentrate than the discovery period, since both the advertisement period anddiscovery period are calculated based on a multiple of an agreed uponpredetermined base value, the advertisement transmission and discoverylistening eventually overlap at time slots 901-903.

As a result, an advertiser and/or a discoverer may independently adjustthe adjustment factor based on the operating conditions of theindividual devices. For example, if it is determined that the battery ofa device is at a low level, the adjustment factor (N) may be increasedto slow the advertisement and/or discovery activities, which in turnreduces further power consumption and channel usage. However, increasingan advertisement period and/or discovery period may also increase thedetection time to catch a particular advertisement message, which leadsto a lower performance.

According to another embodiment, a discovery period is calculated as amultiple of a dwell time (e.g., the period of time during which thedevice is listening for advertisement message), but not a multiple of anadvertisement period. In a particular embodiment, an advertisementperiod is configured to be a multiple of a predetermined base value(e.g., 100 ms) * 2^N, where N could be any integer number; a discoveryperiod is configured to be the predetermined base value * 3^M or 5^M,where M could be any integer number; and a dwell time is configured tobe the predetermined base value (e.g., 100 ms)*(1+10%). Adding 10% tothe dwell time account for inefficiency ensures that the dwell time isstrictly greater than the predetermined base value.

In the table below, the percentage numbers in bracket represent thepercentage of time at least the RF frontend of a device has to be up forthese specific advertisement/discovery periods. The advertisement numberis based on a 2 ms ballpark estimate for the advertisement messagetransmission: waking up the radio, contending for the channel andtransmitting a few hundred us frame. The discovery number is based on a100 ms discovery listen dwell time. The numbers in the main part of thetable indicate how long it will take to discover a device in the worstcase if the advertiser is using the advertisement period in the relevantcolumn header and the discoverer is using the discovery period in therelevant row header. All times are in seconds.

Adv. Period 0.1 0.2 0.4 0.8 Disc. Period (2%) (1%) (.5%) (.25%)  0.1(100%) 0.1 0.2 0.4 0.8  0.3 (33.3%) 0.3 0.6 1.2 2.4  0.9 (11.1%) 0.9 1.83.6 7.2  2.5 (4%) 2.5 5 10 20  2.7 (3.7%) 2.7 5.4 10.4 20.8  8.1 (1.24%)8.1 16.2 32.4 64.8 12.5 (.8%) 12.5 25 50 100 24.3 (.41%) 24.3 48.6 97.2194.4 62.5 (0.0016%) 62.5 125 250 500

A device that is in a static environment or that wishes to drasticallyreduce the battery usage can independently increase its discovery periodand advertisement period, for example, 24.3 seconds and 200 msrespectively. In this example, based on the table above, this ensuresthat the airtime (e.g. time during which the radio is listening and atfull power) for such a device is below 1.5% at the cost of increaseddetection time (48.6 seconds in order to detect another deviceoptionally implementing the same value). “Static environment” refers to,for example, the case of a user staying home for a long period of time,and hence will not encounter change in the wireless operatingenvironment. Similarly, a device with a large battery or which is in adynamic environment (or which detect that it is moving) can alsoindependently decrease its discovery period, for example, to 2.5seconds, which can lead to a fast discovery time. This would be the caseof a plugged device with an AC power. Devices that detect they are in acrowded environment, for example, if they detect more than 15 otheradvertisers or access points (APs), can independently increase theiradvertisement periods, which increases the detection time but reducesnetwork congestion. Increasing advertisement period, for example, to 400ms, could cause detection time to be in the 50 second range for a devicethat is discovering with 12.5 second period, and the air time in thiscase is 1.3%. This would be the case in which a user may be sitting in aconference room or an open space work environment with many cubicles.

Detection of the fact that a user is moving can be done by recording thepresence of a few access points with a reasonably high received signalstrength indicator (RSSI) across multiple discovery periods. Thisrequires a device to cache the basic service set identifiers (BSSIDs) ofthe certain highest RSSI APs that are detected during a discoveryperiod. If there is no high RSSI AP detected, this means that the useris moving fast or is in a WiFi free environment. Advertisement periodand discovery period should be adjusted lower in order to decreasedetection time. If one or more of those high RSSI APs are constantlydetected across several discovery periods (e.g., associated or notassociated, and not roaming), then the user may be sitting at home or ina known place. The discovery period can be set to 200 ms andadvertisement period can be increased to a large value (e.g., 24.3seconds or 62.5 seconds). This user will not take a long time to detectother devices, but will be detected less easily by moving devices. Ifthe environment is crowded, then adjustments have to be made in order toreduce potential congestion, and the advertisement period needs to beincreased. As a result, devices can detect each other by discoveringmore often (e.g., consuming more power) or waiting longer.

FIG. 10 is a flow diagram illustrating a method for advertising aservice according to another embodiment of the invention. Note thatmethod 1000 may be performed by processing logic which may includehardware, firmware, software, or a combination thereof. For example,method 1000 may be performed by service advertisement unit 201 of FIG.8. Referring to FIG. 10, at block 1001, current operating conditions aremonitored by a local device (e.g., advertiser), including batterystatus, network traffic congestion, user behaviors, and types ofservices to be advertised, etc. Based on the operating conditions, atblock 1002, an advertisement period is dynamically adjusted accordingly.In one embodiment, the advertisement period is a configured as amultiple of a predetermined base value as set forth above. At block1003, an advertisement is broadcast or multicast in a network accordingto the adjusted advertisement period, including one or more servicesbeing advertised using the service advertisement and discoverytechniques set forth above. At block 1004, a service request is receivedfrom a remote device in response to the advertisement request, includinga service identifier or indicator that identifies a service to beinquired. In response to the service request, at block 1005, detailedinformation of the requested service is provided via a service responseto the remote device over the network.

FIG. 11 is a flow diagram illustrating a method for discovering aservice according to another embodiment of the invention. Note thatmethod 1100 may be performed by processing logic which may includehardware, firmware, software, or a combination thereof. For example,method 1100 may be performed by service discovery unit 202 of FIG. 8.Referring to FIG. 11, at block 1101, current operating conditions aremonitored by a local device (e.g., discoverer), including batterystatus, network traffic congestion, user behaviors, and types ofservices to be advertised, etc. Based on the operating conditions, atblock 1102, a discovery period is dynamically adjusted accordingly. Inone embodiment, the discovery period is a configured as a multiple of apredetermined base value as set forth above. At block 1103, processinglogic periodically listens in the network according to the adjusteddiscovery period in an attempt to discover a service available in thenetwork. In response to an advertisement received from a remote deviceduring the discovery, at block 1104, a service request is transmitted tothe remote device for inquiring a service advertised in theadvertisement. At block 1105, a service response is received from theremote device in response to the service request including certaindetailed information of the requested service or services.

Coordinated Service Advertisements Embodiments

According to some embodiments, multiple devices that are capable ofadvertising one or more services may coordinate with each other toselect one or more of devices to advertise the services on behalf ofother devices. A device may be selected as a group advertiser accordingto a variety of parameters (e.g., a battery condition, etc.), which ismonitored by monitoring logic of the device. A device may operate as agroup advertiser that advertises its own services and services of otherdevices in the network. A device may also operate as an advertiser foradvertising its own services, as well as an advertisee having one ormore its services advertised by another device. A device may operate asan advertisee only that relies on another device for advertising itsservices.

FIG. 12 is a block diagram illustrating an electronic device accordingto another embodiment of the invention. For example, device 1200 may beimplemented as any one of devices 101-103 of FIG. 1. Referring to FIG.12, similar to device 200 of FIG. 2 or device 800 of FIG. 8, device 1200includes, but not limited to, service advertisement unit 201, servicediscovery unit 202, user interface unit 203, service management unit204, storage device 205 for storing service identifiers 210 and serviceinformation 211, one or more processors or processor cores 206, networkinterface unit 207, memory 208, user interface unit 203 coupled to eachother via bus, interconnect, or mesh 209, and an operating environmentmonitoring unit 801. These components may have identical or similarfunctionalities as those shown in FIGS. 2 and 8 and thus, certainreference numbers are retained from FIGS. 2 and 8 for the purpose ofillustration.

In addition, according to one embodiment, device 1200 further includesadvertiser selection unit 1201 configured to coordinate with otherdevices within a proximity of the network to select one or more devicesas group advertisers that advertise services on behalf of others. Forexample, advertiser selection unit 1201 communicates with advertiserselection units of other devices within a predetermined proximity of thenetwork to select or negotiate one or more devices among them to begroup advertisers. The one or more devices may be determined andselected based on one or more parameters or attributes, such as, forexample, operating conditions and/or user behaviors, which may bemonitored or collected by monitoring unit 801.

For example, when advertiser selection unit 1201 determines that aremote device should be selected as an group advertiser, advertiserselection unit 1201 may instruct service advertisement unit 201 totransmit a service advertisement request message (also simply referredto as an advertisement request) to the selected remote device, such thatthe remote device can advertise the services for device 1200. Unlike anadvertisement which is broadcast or multicast in the network, anadvertisement request may a unicast (e.g., point-to-point) messagerequesting a specific remote device for advertisement. Alternatively, anadvertisement request may be multicast or broadcast in the networkrequesting one or more remote advertisers. In one embodiment, theservice advertisement request sent to the remote advertiser includes anaddress of device 1200 (e.g., media access address or MAC of device1200), a number of service identifiers, actual service identifiers(e.g., hashes), and availability information such as the availabilityschedule of device 1200. As a result, when the services are advertisedby the remote group advertiser, a remote discoverer can directlycommunicate with device 1200 to inquire one or more services that areadvertised by a remote group advertiser, without having to contact theremote group advertiser. Device 1200 may continue advertising its ownservices while a remote group advertiser advertises at least some of theservices on behalf of device 1200.

Alternatively, once a remote advertiser is selected to advertiseservices for device 1200, advertisement selection unit 1201 may instructservice advertisement unit 201 to stop advertising its own services andto transition device 1200 into an advertisee. Furthermore, advertiserselection unit 1201 may simply receive a service advertisement requestfrom a remote device and instruct the service advertisement unit 201 tocarry out the advertisement on behalf of the remote device, as well asits own services. In this situation, an advertisement request is aunicast or multicast message (e.g., specifically directed to one or morespecific devices), rather than a broadcast message (e.g., sent to alldevices in the network).

Embodiments of the present application can be applied in a situationwhere many devices are in range of each other and participating inproximity detection (e.g., in a crowded conference room). In thissituation, scalability is achieved by having devices sharing theiradvertisements in which only a few devices advertise for all others.When two devices see each other (via proximity detection set forthabove) and regardless of the fact that they may share a common serviceidentifier (e.g., hash), one of the devices may request the other tocarry its own advertisement payload, for example, by transmitting adirected advertisement request frame to the other device. Theadvertisement request frame needs not be answered; as long as therequested device is observed to carry the advertisement payload of therequesting device, the requested device is considered to be a groupadvertiser for the requesting device, and the requesting devices thenconsidered as an advertisee.

In one embodiment, a device may operate in one of four states:

-   -   State 0: advertiser (e.g., advertising only for itself).    -   State 1: group advertiser (e.g., advertise for itself and        advertise for some other peers)    -   State 2: advertiser and advertisee (e.g., advertised by at least        one other peer, advertising for itself, and not advertising for        other peers)    -   State 3: advertisee (e.g., advertised by some other peers)

Devices start initially in state 0, in which they are advertising onlytheir own services. This state is default state, and shares the samebasic behavior as described in previous sections. Via participation inthe cooperative advertising algorithm, devices in state 0 may bepromoted to one of the additional cooperative advertising states 1-3.

The algorithm uses only one frame (i.e., the advertisement request),which is a directed frame and can be sent by a device in state 0, state2 or state 3 to a device in state 0 , state 1 or state 2. Whenevermultiple devices are in a range of a high number of other devicesparticipating in the proximity detection, they may enter cooperativeadvertisement. In one embodiment, each device implementing cooperativeadvertisement attempts to find a given number of advertisers that arecapable of carrying its own advertisement payloads, such as, forexample, two or three advertisers. When an advertisee is advertised byenough peers, it may stop transmitting its own advertisement frames andis then only discoverable through its remote group advertisers. Arequest for advertisement may be valid for a fixed period of time (e.g.,several minutes) and may then be required to renew.

According to one embodiment, cooperative advertisement takes place onlywhen two devices are able to see each others, i.e. they are bothoperating in state 0, state 1 or state 2. In one embodiment, a devicemay be elected as an group advertiser for another device based on atleast some of the following considerations:

-   -   1. A device may be selected as a group advertiser if the device        is not advertising for more than a predetermined number of peers        (e.g., 16 peers);    -   2. A device may be selected as a group advertiser if the device        is currently advertising for the highest number of other peers;    -   3. A device may be selected as a group advertiser if the device        is currently advertised by the smallest number of peers;    -   4a. A device may be selected as a group advertiser if the device        advertises the highest number of services in total; and/or    -   4b. A device may be selected as a group advertiser if the device        has the longest battery life remained;    -   5. A device may be selected as a group advertiser if the device        has the highest number of service IDs; and    -   6. A device may be selected as a group advertiser if the device        has the highest MAC address.

In order to elect one device the above clauses are evaluated in asequential order and/or in parallel. For example, clauses 4a and 4b maybe evaluated concurrently. That is, a device that has an abnormally highnumber of service IDs would most likely be selected as a groupadvertiser. If the number of service IDs is about the same, then batteryusage becomes a prime factor. If on the other hand, a devices has aninfinite battery life (e.g., plugged into an AC outlet), then it wouldalso likely be elected as a group advertiser. In one embodiment, batteryusage may be coded with two numbers representing the class of device andthe amount of up time remaining on the battery. Optimizing thetopological distribution of the cooperative advertisements is one of thegoals of the algorithm. This goal is to converge to a situation where asmall number of group advertisers are carrying extra advertisementpayloads for other advertisees, which will then stop advertisingthemselves (i.e. entering state 3). The advertisers of an advertisee maybe spatially distributed around and/or close to the advertisee (e.g.,uniform spatial distribution of advertisers).

The uniformity of spatial distribution is achieved because multiplegroup advertisers sharing a common advertisee should not be able to seeeach other or may see each other only with a very low RSSI, i.e. theyare not close to each other. Whenever they are able to see each otherwith a certain level of RSSI (e.g., more than a half range RSSI) andthey share a common advertisee, according to one embodiment, one of thegroup advertisers may drop the additional payload for that commonadvertisee and stop being an advertiser for that advertisee. Inaddition, amongst its surrounding peers matching clauses 1-6 above, adevice is free to choose the closest one (e.g., based on RSSI) as itspotential group advertiser.

According to some embodiments, advertisements are finite in time andneed to be renewed periodically, for example, every few minutes or so.They are renewed when the corresponding advertisee transmits a newrequest to a group advertiser. Requests cannot be retransmitted to agiven peer within a minimum amount of time, for example, within lessthan a few minutes. A device may ask (e.g., sending an advertisementrequest) to be advertised by another peer whenever the RSSI of frames itreceives from the peer falls between a halfway and a maximum ranges,i.e. advertiser and advertisee are relatively close to each other. Thishelps avoid situations when third party devices are in range of theadvertiser but not in range of the advertisee.

In one embodiment, a device may ask multiple peers to act as groupadvertisers, provided those peers meet clauses 1-6 above. Clauses 1-6are designed so as within any pair of devices in range of each other,only one of the devices can potentially be elected as group advertiserfor the pair. Group advertisers in state 3 in a half RSSI range of eachother may compare their additional payloads and drop the redundantadditional advertisement payloads. That is, if two group advertisers ina half RSSI range of each other share a common advertisee, then one ofthe advertisers should drop the advertisement for the advertisee. Theelection of a device dropping as an advertiser may also follow clauses1-6 above. That is, a group advertiser that carries the highest numberof peers (e.g., up to 16) will keep the common advertisee whereas thegroup advertiser that carries the lowest number of peers will drop theadvertisee. Note that this does not require any frame exchanged. Thatis, the elected group advertiser will keep the shared advertisee and donothing; the other one will silently drop the advertisee. Bothadvertisers stay in state 3.

In one embodiment, group advertisers in state 1 in a half RSSI range ofeach other that do not share a common advertisee may also choose tocooperate, i.e., one of the group advertisers is elected as a groupadvertiser and one is elected as advertisee for the pair. The advertiseeenters state 2 (e.g., dropping its own advertisees) and if theadvertisee reaches three peers, it will then drop its own payload andenters state 3 (e.g., it stops advertising altogether). The advertiserof the pair may start carrying the advertisee's advertisement payload,but not the advertisee's additional payload. This requirement ensuresthat an advertisee's additional payload is not transferred from a groupadvertiser originally located close to it to a group advertiser thatmight be located far from it. The third party peers that have beendropped now need to find a new advertiser or become advertisersthemselves. Note that this also does not require any frame exchanged.Dropped peers in state 2 may find another group advertiser and remain intheir current state, or they may transition to state 0 and operatewithout a group advertiser. A device in state 3 that finds itself in asituation where it cannot find at least 2 group advertisers carrying itsadvertisement payload may enter state 2 and resume broadcasting its ownadvertisements. A device in state 3 that can't find any groupadvertisers carrying its advertisement payload may enter state 0 andresume broadcasting its own advertisements. These two transitions canoccur when a group advertiser goes out of range, is disabled, and/orwhen the advertisement request times out, and all group advertisersaround it are at maximum capacity and/or when there are not manyadvertisers surrounding it. Alternatively, a device in state 3 may thatcannot find sufficient group advertisers carrying its advertisementpayload may select new group advertisers using the rules above, and ifsuccessful may remain in state 3.

For example, a “good” situation is when one group advertiser carries upto 16 additional payloads and an advertisee's payload is carried by 2surrounding group advertisers. The number of advertisement framestransmitted on the channel is then globally divided by 16; hence therewill be a much smaller probability of collisions. The total transmittedpayload (i.e. byte per second) is divided by 8.

FIGS. 13A-13C are transitional diagrams illustrating examples oftransitions of devices among operating states according to someembodiments of the invention. Referring to FIG. 13A, it is assumed thatdevices 1301-1308 are operating within a predetermined proximity, whichis detected using certain techniques described above. In this example,devices 1301-1302 are operating as group advertisers in state 1; devices1303-1307 are operating as advertisees in state 3; and device 1308 isoperating as an advertiser & advertisee in state 2. As can be seen inFIG. 13A, device 1301 is selected as a group advertiser for device 1308,as well as devices 1303 and 1305. Device 1302 is selected as a groupadvertiser for devices 1304 and 1305-1307. It is also assumed thatdevices 1301-1302, which are operating in state 1, are close to eachother and are able to see each other (e.g., above certain RSSI level).

Based on the above advertiser election algorithm, since device 1302 hasa higher number of advertisees (e.g., devices 1304 and 1305-1307) thandevice 1301 (e.g., devices 1303, 1305, and 1308), between devices1301-1302, device 1302 is selected as a group advertiser for device1301. As a result, as shown in FIG. 13B, device 1301 transitions fromstate 1 to state 2, and it no longer operates as an advertiser fordevice 1308. Subsequently, in FIG. 13C device 1308 becomes a groupadvertiser in state 1 and device 1301 becomes an advertisee advertisedby devices 1302 and 1308 due to clause 3 above (e.g., the smallestnumber of advertisees).

When an advertiser carries an advertisement for an advertisee, a groupadvertisement message is created that includes an advertisement for itsown services and the services of the advertisee. FIG. 14 is a blockdiagram illustrating a group advertisement message according to oneembodiment of the invention. Referring to FIG. 14, group advertisementmessage 1400 includes advertisement message 1401 for the advertiseritself (e.g., advertisement message for its own services), which isidentical or similar to advertisement message 500 of FIG. 5. Inaddition, compound advertisement message 1400 includes additionaladvertisement messages 1402-1404, each corresponding to an advertisee.In one embodiment, advertisement message 1410 for an advertisee (e.g.,messages 1402-1404) includes address (e.g., MAC address) of theadvertisee 1411, number of service identifiers 1412 and actual serviceidentifiers (e.g., hashes) 1413, and the availability schedule 1414 ofthe advertisee. As a result, although advertisement message 1410 isadvertised by an advertiser, other devices may respond to theadvertisement by directly communicating with the advertisee. Note thatthe formats of advertisement messages as shown in FIG. 14 are describedfor illustration purposes only; other formats may also be applied.

Also note that although a local device may select a remote device to beits group advertiser based on the operating condition of the localdevice in view of the operating condition of the remote device,according to one embodiment, the remote device may reject or ignore theadvertisement request based on its own determination or assessment ofthe operating condition of the remote device. In this situation, unlessan acknowledgement is received from the remote device, the local devicemay have to monitor traffic (e.g., service advertisements) in thenetwork to determine whether the selected remote device actually carriesout the advertisement on behalf of the local device. The local devicemay have to select another remote device if the remote device rejects orignores the advertisement request.

FIG. 15 is a flow diagram illustrating a method for advertising aservice according to another embodiment of the invention. Note thatmethod 1500 may be performed by processing logic which may includehardware, firmware, software, or a combination thereof. For example,method 1500 may be performed by advertisement unit 201 and/or advertiserselection unit 1201 of FIG. 12. Referring to FIG. 15, at block 1501, alocal device listens in a wireless network to determine one or moreremote devices that are capable of advertising one or more services inthe network. At block 1502, the local device compares certainpredetermined operating statistics and/or configurations of the localand remote devices. At block 1503, the local device selects one or moreremote devices based on the comparison to advertise one or more servicesof the local device. At block 1504, the local device transmits anadvertisement request to the selected remote devices requestingadvertisement on behalf of the local device, including identifiers(e.g., hashes) of one or more services to be advertised. The device thenwaits to see whether the request was accepted by listening for itsservices in the remote device's next group advertisement message, or bywaiting for a successful advertisement response at block 1505. If therequest fails, the local device checks whether there are other remotedevices that could serve as a group advertiser. If so, it goes to block1501 and retries the procedure with a different device. If not, it stopsthe procedure. If the request succeeds, it continues to block 1505. Atblock 1505, optionally the local device terminates advertisement of itsown services and relies on the selected remote devices for advertisingits services.

FIG. 16 is a flow diagram illustrating a method for advertising aservice according to another embodiment of the invention. Note thatmethod 1600 may be performed by processing logic which may includehardware, firmware, software, or a combination thereof. For example,method 1600 may be performed by advertisement unit 201 and/or advertiserselection unit 1201 of FIG. 12. Referring to FIG. 16, at block 1601, anadvertisement request is received from a remote device, includingservice IDs for one or more services to be advertised. At block 1602,the device compares certain predetermined operating statistics and/orconfigurations of the current and requesting device to see if therequest was valid. If not, it may transmit an advertisement responseindicating failure at block 1606 and then goes to block 1602. If so, itmay transmit an advertisement response indicating success and thencontinues to block 1604. At block 1604, processing logic constructs agroup advertisement message having advertisement of a local service andadvertisement of the requested one or more services of the remotedevice. At block 1605, the local device periodically broadcasts thecompound advertisement frame in the network.

FIG. 17 is a flow diagram illustrating a method for selecting a deviceas a group advertiser according to one embodiment of the invention.Referring to FIG. 17, at block 1701, a device may be selected as a groupadvertiser if the device is not currently advertising for more than apredetermined number of other peers. At block 1702, a device may beselected as a group advertiser if the device is currently advertisingfor the highest number of other peers. At block 1703, a device may beselected as a group advertiser if the device is currently beingadvertised (e.g., as an advertisee) by the fewest number of other peers.At block 1704, a device may be selected as a group advertiser if thedevice currently advertises the highest number of services in total oralternatively, if the device has the longest remaining battery life. Atblock 1705, a device may be selected as a group advertiser if the devicecurrently has the highest number of services IDs. At block 1706, adevice may be selected as a group advertiser if the device currently hasthe highest MAC (media access control) address. Note that operationsinvolved in blocks 1701-1706 may be performed in sequence and/or inparallel, with no particular order. Other factors may also be consideredherein.

Techniques described throughout this application can be applied tovarious scenarios or situations. Services can be advertised and/ordiscovered based on proximity detection of the portable devices usingsome of the techniques described above. This feature allows users ofportable devices to advertise one or more services permanently through awireless network protocol and to detect whether the portable devicesmove within a range of another portable device that is advertising oneof those services. The term of “permanently” is referred to the factthat the advertisement can be open or available for a period of timewithout further interaction from the local user of the device (e.g., theadvertiser).

For example, a gamer (e.g., chess or poker player, etc.) can easilyconnect to whatever internet site or gaming social network and playagainst any available opponent. Such a user may never meet the opponentin person, but knows (discovers) through the network. In this scenario,a user of a portable device looking for opponents would broadcast anadvertisement for a specific game in the network. The advertisement maybe generated by a gaming application and can include additionalinformation such as ranking of the user as a player, desired ranking ofan opponent, desired type of game, etc. As soon as users walk into arange of another person who is advertising the same game, both users maybe alerted (e.g., by an alarm, vibration, etc.) and can connect witheach other for playing. Proximity also means that users play with otherusers they will actually be able to meet in person vs. playing againstrandom opponents across the network.

The techniques described above can also be applied in sharing content orfiles permanently (e.g., available for a period of time). This issimilar to exporting certain content (e.g., pictures) from a portabledevice, but it is done in an ad-hoc fashion over a peer-to-peer link.For example, a user participating in a conference (or a party or presentin a university campus) can share a picture or a document, and can keepthis sharing “open” for a period of time (e.g., a day or the entireduration of the conference or party). Any colleague or friend that canbe authenticated/paired with the user's device can walk by (e.g., withinthe proximity) and access (e.g., download) the picture or document.

If the owner of the shared content allows it, and dependent upon certainconfiguration of the corresponding device (e.g., advertiser), thecontent can be shared without requiring the owner's interaction (e.g.,alerting or asking a permission, etc.) to create a peer-to-peerconnection. For the user point of view, this means that one can snap apicture of an event and walk by all day continuously broadcasting thepicture.

When two or more devices are coupled to each other via a network andwithin a predetermined proximity, devices can discover each other overthe network as well as the services available to each other. If devicescan determine that they support a common multi-device capableapplication (e.g., by a matching the corresponding service ID), such asa multi-player game, each of the devices may be configured to performone or more distributed functionalities of the multi-device capableapplication. A distributed functionality is a functionality of themulti-device capable application that is assigned to one or moredifferent devices, which may be perform the distributed functionalitysubstantially simultaneously. The distributed functionalities mayinclude input, output, and computing, etc. Each device may collaboratewith other devices to perform its distributed functionalities. Moreover,some of the devices may collaborate with each other to perform the samedistributed functionalities. In other words, each device may take up aspecific role in performing the multi-device capable application, andhas a relationship with other devices based on its role. Furthermore,such roles and relationships may be dynamically modified in response toaddition of a device to the network, removal of devices from thenetwork, current status of the execution of the application, and/or userinputs, etc.

In this example, at least part of a multi-device capable application isshared among multiple devices over a network. To share the multi-devicecapable application, all or part of the multi-device capable applicationmay be previously installed on some or all devices in the network, wherethe multi-device capable application may be identified by a service IDset forth above. Alternatively, one or more devices may transmit all orpart of the multi-device capable application to the other devices in thenetwork in order to share the multi-device capable application. As aresult, the distributed functionalities are performed in a collaboratedfashion. Further detailed information concerning techniques forcollaborated distributed functionalities by multiple devices can befound in co-pending U.S. patent application Ser. No. 12/479,586,entitled “Multifunctional Devices as Virtual Accessories,” filed Jun. 5,2009, which is incorporated by reference herein in its entirety.

Example of Data Processing System

FIG. 18 shows an example of a data processing system which may be usedwith one embodiment of the present invention. For example, system 1800may be implemented as any one of devices 101-103 as shown in FIG. 1. Thedata processing system 1800 shown in FIG. 18 includes a processingsystem 1811, which may be one or more microprocessors, or which may be asystem on a chip of integrated circuit, and the system also includesmemory 1801 for storing data and programs for execution by theprocessing system. The system 1800 also includes an audio input/outputsubsystem 1805 which may include a microphone and a speaker for, forexample, playing back music or providing telephone functionality throughthe speaker and microphone.

A display controller and display device 1807 provide a visual userinterface for the user; this digital interface may include a graphicaluser interface which is similar to that shown on an iPhone® phonedevice, an iPad device, or on a Macintosh computer when runningoperating system software. The system 1800 also includes one or morewireless transceivers 1803 to communicate with another data processingsystem. A wireless transceiver may be a WiFi transceiver, an infraredtransceiver, a Bluetooth transceiver, and/or a wireless cellulartelephony transceiver. It will be appreciated that additionalcomponents, not shown, may also be part of the system 1800 in certainembodiments, and in certain embodiments fewer components than shown inFIG. 18 may also be used in a data processing system.

The data processing system 1800 also includes one or more input devices1813 which are provided to allow a user to provide input to the system.These input devices may be a keypad, a keyboard, a touch panel, or amulti touch panel. The data processing system 1800 also includes anoptional input/output device 1815 which may be a connector for a dock.It will be appreciated that one or more buses, not shown, may be used tointerconnect the various components as is well known in the art. Thedata processing system shown in FIG. 18 may be a handheld computer or apersonal digital assistant (PDA), or a cellular telephone with PDA likefunctionality, or a handheld computer which includes a cellulartelephone, or a media player, such as an iPod, or devices which combineaspects or functions of these devices, such as a media player combinedwith a PDA and a cellular telephone in one device. In other embodiments,the data processing system 1800 may be a network computer or an embeddedprocessing device within another device, or other types of dataprocessing systems which have fewer components or perhaps morecomponents than that shown in FIG. 18.

At least certain embodiments of the inventions may be part of a digitalmedia player, such as a portable music and/or video media player, whichmay include a media processing system to present the media, a storagedevice to store the media and may further include a radio frequency (RF)transceiver (e.g., an RF transceiver for a cellular telephone) coupledwith an antenna system and the media processing system. In certainembodiments, media stored on a remote storage device may be transmittedto the media player through the RF transceiver. The media may be, forexample, one or more of music or other audio, still pictures, or motionpictures.

The portable media player may include a media selection device, such asa click wheel input device on an iPod®, or iPod Nano® media player fromApple Inc. of Cupertino, Calif., a touch screen or multi-touch inputdevice, pushbutton device, movable pointing input device or other inputdevice. The media selection device may be used to select the mediastored on the storage device and/or a remote storage device. Theportable media player may, in at least certain embodiments, include adisplay device which is coupled to the media processing system todisplay titles or other indicators of media being selected through theinput device and being presented, either through a speaker orearphone(s), or on the display device, or on both display device and aspeaker or earphone(s).

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, transferred, combined, compared, and otherwisemanipulated. It has proven convenient at times, principally for reasonsof common usage, to refer to these signals as bits, values, elements,symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as those set forth in the claims below, refer to the actionand processes of a computer system, or similar electronic computingdevice, that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

Embodiments of the invention also relate to an apparatus for performingthe operations herein. This apparatus may be specially constructed forthe required purposes, or it may comprise a general-purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a computerreadable medium. A machine-readable medium includes any mechanism forstoring information in a form readable by a machine (e.g., a computer).For example, a machine-readable (e.g., computer-readable) mediumincludes a machine (e.g., a computer) readable storage medium (e.g.,read only memory (“ROM”), random access memory (“RAM”), magnetic diskstorage media, optical storage media, flash memory devices, etc.), etc.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the required method operations. The requiredstructure for a variety of these systems will appear from thedescription above. In addition, embodiments of the present invention arenot described with reference to any particular programming language. Itwill be appreciated that a variety of programming languages may be usedto implement the teachings of embodiments of the invention as describedherein.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary embodiments thereof. Itwill be evident that various modifications may be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the following claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1. A method for advertising a service, the method comprising: in a localdevice, performing operations for: based on a condition of the localdevice, dynamically adjusting a time period between a broadcast of aservice advertisement and an availability window during which the localdevice monitors for service requests; broadcasting the serviceadvertisement in a wireless network, the service advertisement includingone or more service identifiers (IDs) identifying one or more servicesbeing advertised and an availability schedule of the device, wherein theavailability schedule comprises a specification of the availabilitywindow; reducing power to at least a portion of the local device for atime period after the service advertisement has been broadcast andbefore the availability window; restoring power to the at least theportion of the local device and monitoring for service requests in thewireless network during the availability window; and in response toreceiving a service request from a remote device during the availabilitywindow, transmitting a service response to the remote device, theservice response having detailed information associated with one or moreservices identified by one or more service IDs in the service request.2. The method of claim 1, wherein each service ID is represented by ahash value identifying a service potentially available from the localdevice.
 3. The method of claim 1, wherein the service advertisementincludes information indicating a number of services IDs and actualservices IDs contained within the service advertisement, eachrepresenting a service potentially available from the local device. 4.The method of claim 1, wherein the availability schedule of the localdevice includes a next availability window starting time and a durationof the availability window upon which the local device is configured tolisten to service requests from the wireless network.
 5. The method ofclaim 4, wherein the next availability window is represented by a timeoffset from a time of broadcasting the advertisement to the startingtime of the next availability window, upon which the local device isconfigured to listen for a period of time specified by the duration ofthe availability window.
 6. The method of claim 1, wherein the conditioncomprises a battery status for the local device.
 7. The method of claim1, wherein the condition comprises a behavior for a user for the localdevice.
 8. The method of claim 1, wherein the condition comprises a typeof service for at least one of the one or more services.
 9. Anon-transitory machine-readable storage medium having instructionsstored therein, which when executed by a machine, cause the machine toperform a method for advertising a service, the method comprising: in alocal device, performing operations for: based on a condition of thelocal device, dynamically adjusting a time period between a broadcast ofa service advertisement and an availability window during which thelocal device monitors for service requests; broadcasting the serviceadvertisement in a wireless network, the service advertisement includingone or more service identifiers (IDs) identifying one or more servicesbeing advertised and an availability schedule of the device, wherein theavailability schedule comprises a specification of the availabilitywindow; reducing power to at least a portion of the local device for atime period after the service advertisement has been broadcast andbefore the availability window; restoring power to the at least theportion of the local device and monitoring for service requests in thewireless network during the availability window; and in response toreceiving a service request from a remote device during the availabilitywindow, transmitting a service response to the remote device, theservice response having detailed information associated with one or moreservices identified by one or more service IDs in the service request.10. The machine-readable storage medium of claim 9, wherein each serviceID is represented by a hash value identifying a service potentiallyavailable from the local device.
 11. The machine-readable storage mediumof claim 9, wherein the service advertisement includes informationindicating a number of services IDs and actual services IDs containedwithin the service advertisement, each representing a servicepotentially available from the local device.
 12. The machine-readablestorage medium of claim 9, wherein the availability schedule of thelocal device includes a next availability window starting time and aduration of the availability window upon which the local device isconfigured to listen to service requests from the wireless network. 13.The machine-readable storage medium of claim 12, wherein the nextavailability window is represented by a time offset from a time ofbroadcasting the service advertisement to the starting time of the nextavailability window, upon which the local device is configured to listenfor a period of time specified by the duration of the availabilitywindow.
 14. A portable device, comprising: a wireless transceiver; apower management unit coupled to the wireless transceiver, wherein thepower management unit is configured to: based on a condition of theportable device, dynamically adjust a time period between a broadcast ofa service advertisement and an availability window during which theportable device monitors for service requests; reduce power to at leasta portion of the portable device for a time period after the serviceadvertisement has been broadcast and before the availability window;restore power to the at least the portion of the portable device andduring the availability window; and a service advertisement unit coupledto the wireless transceiver to broadcast the service advertisement in awireless network via the wireless transceiver, the service advertisementincluding one or more service identifiers (IDs) identifying one or moreservices being advertised and an availability schedule of the portabledevice, wherein the availability schedule comprises a specification ofthe availability window, and wherein in response to a service requestreceived from a remote device during the availability window, theservice advertisement unit is configured to transmit a service responseto the remote device, the service response having detailed informationassociated with one or more services identified by one or more serviceIDs in the service request, wherein the portable device is configured tomonitor for service requests in the wireless network during theavailability window.
 15. A method for discovering a service, the methodcomprising: in a local device, performing operations for: receiving aservice advertisement from a remote device over a wireless network, theservice advertisement including one or more service identifiers (IDs)identifying one or more services advertised by the remote device,wherein the service advertisement further includes an availabilityschedule of the remote device, wherein the availability schedulecomprises a specification of an availability window during which theremote device monitors for service requests, and wherein the remotedevice, based on a condition of the remote device, dynamically adjusts atime period between a broadcast of the service advertisement and theavailability window; reducing power to at least a portion of the localdevice after receiving the service advertisement and before theavailability window specified by the availability schedule of the remotedevice; restoring power to the at least a portion of the local deviceduring the availability window of the remote device; and in response tothe service advertisement, transmitting, by the local device, a servicerequest to the remote device to inquire one or more services in theadvertisement, the service request including one or more service IDsassociated with the one or more services being inquired.
 16. The methodof claim 15, wherein each service ID is represented by a hash valueidentifying a service potentially available from the remote device. 17.The method of claim 15, wherein the service advertisement includesinformation indicating a number of services IDs and actual services IDscontained within the advertisement, each representing a servicepotentially available from the remote device.
 18. The method of claim15, wherein the availability schedule of the remote device includes anext availability window start and a duration of the availability windowupon which the remote device is configured to listen to service requestsfrom the wireless network.
 19. The method of claim 18, wherein the nextavailability window is represented by a time offset from a time ofbroadcasting the service advertisement to the starting time of the nextavailability window, upon which the remote device is configured tolisten for a period of time specified by the duration of theavailability window.